The field of the invention concerns blood sampling devices which provide a visual indication of venipuncture.
Blood sampling needles currently in commercial use do not allow the phlebotomist (person drawing blood) to know when the needle is properly inside the vein. This is especially a problem with small or tough veins.
A method often used involves watching for the presence of blood dripping from the needle point which is designed for penetration of the stopper of an evacuated blood collection container. This is messy, and is considered traumatic to the patient or donor.
Another method involves actually trying to draw a blood sample with an evacuated collection tube. If this fails, the phlebotomist still does not know for sure if the vein is improperly punctured or if the vacuum in the collection tube might be dissipated.
The utilization of a porous filter which permits the flow of air more readily than blood is known to the art. Commonly assigned U.S. Pat. Nos. 3,864,979, and 4,016,879 are examples of blood sampling devices having such filters. These filters have been advantageously applied for enabling a nurse or physician to readily determine whether the selected vein has been pierced and entered.